A binary Code which is Used in Communications

(Source: http://slideplayer.com/slide/6978766/)

A non-return-to-zero (NRZ) is a binary code which is used in communications. It is commonly applied for both synchronous and asynchronous of data transferring. These transmissions are slow speed communications interfaces.

As defined by Rouse (2011) that NRZ has two numeral codes of one (1) and zero (0). The data are transformed in these binary codes, then transmitted through Direct Current (DC) voltage.

One (1) usually represents a positive voltage or at least a zero value of voltage, called as high state logic of NRZ. While zero (0) usually represents a negative voltage or lower value of positive voltage, but no neutral value of voltage. Zero binary also called as lower state logic of NRZ.

Example values of binary that relevant to voltages are:

Logic 0 = -7 volts --- a negative voltage

Logic 1 = +7 volts --- a positive voltage

Logic 0 = 0.7 volts --- a lower value of positive voltage

Logic 1 = 0.0 volts --- a zero value of voltage

Now, we have a question: “What are the various problems that could arise in Non-Return to Zero (NRZ) encoding if a continuous stream of 0s or 1s is sent? “

First, it will create a problem on the receiver end. Second, we have difficulty to calculate the number of 0s or 1s in the sequences. There could potentially be thousands of 1's or 0's in sequence. Thus, these two problems generate a lack of transition. 

Then, as said by Sanghi (2017) that these problems occur because “the clock synchronization is lost due to lack of any transitions.” To avoid the problems, “Non Return to Zero(NRZ) NRZ codes should share the property that voltage level is constant during a bit interval. High level voltage = bit 1 and Low level voltage = bit 0.”

References

Rouse, M. 2011. NRZ (non-return-to-zero). Retrieved from http://whatis.techtarget.com/definition/NRZ-non-return-to-zero

Sanghi, D. 2017. Data Encoding. Computer Networks (CS425). Retrieved from https://www.cse.iitk.ac.in/users/dheeraj/cs425/lec03.html

Introduction to Asynchronous Transfer Mode (ATM) and Ethernet

Ethernet Vs ATM (http://slideplayer.com/slide/249359/)

          First, the selling point of ATM (Asynchronous Transfer Mode) is quality service which means high-speed with 4 types of service levels. Second, the Ethernet is the most popular LAN (Local Area Network) technology today with over 120 million hosts. The rate of transfer is 10Mbps for the Ethernet.

          Moreover, the comparison between ATM (Asynchronous Transfer Mode) and ETHERNET on the following aspects:

# Bandwidth. Previously, ATM is expected to allow true broadband networking for the future. Today, we know that Ethernet is still a hot technology of LAN (Local Area Network). Ethernet have brought more bandwidth to the network technology.

# Scalability. ATM uses both WAN (Wide Area Network) and LAN (Local Area Network technologies, but ATM is more fit with WAN. However, Ethernet is based mainly on LAN. In the future, Ethernet may use WAN as well.

#Interoperability. Gigabit Ethernet is version of Ethernet, the technology delivers data with speed of 1000 Mbps with fiber-optic cables. However, the operation concept of LAN in Ethernet will not be changed. Moreover, ATM LANE has been developed in order to be properly pursued in old LAN, and easily operated on the desktop. Thus, LAN interoperates with ATM technology.

#Quality of Service

ATM is the top network system to transport data, voice and video until now, thus quality of service is the best. Compared to Ethernet, increasing the speed (bandwidth) of Ethernet could be mean as increasing quality of service.

          Both ATM and Ethernet have their own merit in “high speed” internet technologies. They will compete in the long terms with no one had signs to disappear in the near future. It is mean that quality of service will improve, and benefit for customers.

Standards Used and Features of Mobile Telephones from 1G to 4G

Mobile phone, just for illustration (https://myupdatestudio.com)

Since first generation in 1980’s, mobile telephone has evolved from 1G to 4G, and even 5G is coming soon worldwide. The improvement from 1G to 4G is relating to transmission band, frequency band and services. 

The development of Mobile telephone is not only to its technology, but also increasing number of its users. As mentioned by Sharma (2013) that the number of mobile cellular subscribers are four times than fix telephone lines, and the trend is increasing in recent years. Thus, technology efficiency is important.  

The new generation of Cell Phone bring new technology and high data rates than the older generation (Agrawal et al, 2015). The increasing of wireless phone is following by highly requirement for better features and standard uses. 

In respect to Standards used and Features, the different of Mobile Telephones 1G, 2G, 3G and 4G are following (Agrawal et al, 2015 and Sharma. 2013): 

1G	2G	3G	4G
Advantages: 1)Analog system 2)Cordless Disadvantages: 1)Voice only, no data communication 2)Slow speed and low capacity 3)Less secure	Advantages: 1) Enhanced efficiency 2) Improved system capacity 3) Voice and data services. 4) Enhanced security Disadvantages: 1) does not support high data rates 2) Weaker digital signal. 3)Unable to handle complex data.	Advantages: 1)Supports multimedia 2)Value added services like television, GPS and video conferencing.   3)High speed internet  4) Increased capacity.  Disadvantages: 1)Expensive Cost of upgrading 3G devices  2)Power consumption is high. 3)Expensive base station	Advantages: 1)High efficiency and High voice quality. 2)Easily access internet, streaming media etc 3)Simple protocol architecture. 4)Efficient multicast/broadcast. Disadvantages: 1)Higher data prices  2)very expensive and hard to implement 3)Complex hardware. 4)Power usage is more.

References

Agrawal, J., Patel, R., Mor, P., Dubey, P and Keller, J.M. (2015). Evolution of Mobile Communication Network: from 1G to 4G. International Journal of Multidisciplinary and Current Research Vol.3 (Nov/Dec 2015 issue). Pp.1100-1103

Sharma. P. (2013). Evolution of Mobile Wireless Communication Networks-1G to 5G as well as Future Prospective of Next Generation Communication Network. International Journal of Computer Science and Mobile Computing Vol.2 Issue. 8, August- 2013, pg. 47-53

Different between the Two Switching Methods in Transfer Data

Illustration of circuit and packet switching (http://www.differencebetween.net) 

In sending data from one device (sender) to another certain address of device (receiver), we use a method called as switching. Two switching method generally used in the market, they are Circuit Switching and Packet Switching. 

Point to point connections are established between receiver and sender to transmit data in circuit switching. We could find easily an example of the circuit switching in the daily life which is cable telephone. No broken line while we are making telephone call.  

When data are divided and sent into small packets then we call as packet switching. Each unit packet has header that contain destination address and source of data. When small unit data reach address, then data are assembled as an original one. Two examples of packet switching are IP or TCP and Frame Relay. 

As reported by Tech (2017) the different between Circuit Switching and Packet Switching are following (please see Table at below):

Differences
Circuit Switching	Packet Switching
1. Packets use the same path	Packets travel independently
2. Reserve the entire bandwidth in advance	Does not reserve
3. Physical path between source and destination	No physical path
4.Bandwidth wastage	No Bandwidth wastage

Four simples different between Circuit Switching and Packet Switching

Reference

Tech, A. 2017. Packet Switching vs. Circuit Switching. Retrieved from www.apposite-

tech.com/blog/uncategorized/packet-switching-vs-circuit-switching/

Uplink and Downlink Transmission in Satellite Communication

Uplink and Downlink Transmission (http://techbooksforfree.com)  

Two ways of transmissions in satellite communications are Uplink and Downlink. We call a downlink if communication from a satellite down to ground receivers or stations. Contrary, we call an uplink if communication is going from ground receivers up to a satellite. 

Commercially, many companies provided both downlink and uplink services. But, several companies either sell uplink or downlink only. Corporations such as telephone companies, wireless networks, television stations and other relate communication corporations buy uplink and downlink services to serve their customers.  

Rouse (2007) gave three examples of commonly frequency bands in satellite links, they are Ku, Ka and C bands. Please see the Table below:

Frequency Band	Downlink	Uplink
C	3,700-4,200 MHz	5,925-6,425 MHz
Ku	11.7-12.2 GHz	14.0-14.5 GHz
Ka	17.7-21.2 GHz	27.5-31.0 GHz

From the Table, we could examine that uplink frequency is higher than downlink one. Several reasons why this happen are following:

1.Stations on the earth have greater power, thus able to send higher frequencies to satellites (uplink)

2.Higher frequency signals could eliminate ionized particles at Ionosphere, thus higher frequencies of uplinks more effective than lower ones to reach satellite from ground stations.

3.Since satellites have lower power, because using of solar panels, thus lower frequencies is effective from Satellites to ground stations (downlink). 

In conclusion, each of Uplinks and Downlinks has own effectives in communications. Downlink with lower frequency is more precious than using higher frequency, on the contrary, Uplink is advantage to use higher frequencies. 

Reference

Rouse, M. (2007, May).” downlink and uplink.” Retrieved from https://searchmobilecomputing.techtarget.com/definition/downlink-and-uplink

Technique for Checking the Burst Error

A cyclic redundancy check (https://ccm.net) 

W. Wesley Peterson created a cyclic redundancy check (CRC) in 1961 (Revolvy, 2018). Then, Peterson had published his works that related to CRC in 1975 and won Japan Prize in 1999. CRC is one of well-known technique for checking the burst error in communication. It is popular because CRC is a simple method to be implemented in binary hardware and a good technique to detect errors caused by noise in the channels during communication.  

As described by Sang (2015) that by using CDC, check bits could be attached with sending messages, then receiver could agree or not with data sending or determine whether data have error or not or data have been corrupted or not. If the receiver found error in transmission, then receiver would ask the sender to re-send the messages. In addition to digital networks, CDC can also be applied in storage devices. 

Both sender and receiver apply the same a 16- or 32-bit polynomial for transmission and appending data (Rouse, 2010). Data will be sent and received successfully, if both sender and receiver reach agreement, if not, the receiver will ask sender to send the data again, and again until accomplish the goal of transmission. 

Now, if there is question “why the CRC is put in the trailer rather than in the header of the frame?” The answer is that by being put in the trailer, the computation of CRC is less expensive when the bits of packet arrive. Another advantage that hardware could determine whether the CRC is correct or not, so transmission could be faster and without delaying.  

References 

Revolvy. 2018. W. Wesley Peterson. Retrieved from https://www.revolvy.com/main/index.php?s=W.%20Wesley%20Peterson 

Rouse, M. 2010. cyclic redundancy checking. Retrieved from http://searchnetworking.techtarget.com/definition/cyclic-redundancy-checking 

Sang, SJ. 2015. Design and implementation of cyclic redundancy check in algorithm. Part of publication in  Computing, Control, Information and Education Engineering. Taylor and Francis group, London. Pp.405-409

How to Minimize a Crosstalk in Transmissions?

Crosstalk in Transmissions (http://actelis.com/technology-2) 

Before 1881, the quality of telephone decrease when telephone lines were run close to electrical lines. The problem generally called as “crosstalk.” As defined by Rouse (2005) that Crosstalk is “a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit.” 

This electromagnetic interference could cause microcircuits malfunctions in a such we could hearing a conversation from another telephone. How to minimize crosstalk or electro-magnetic interference? The easy answer is by application of a twisted-pair wires. 

Two separate enclosed cables are intertwined to make a twisted pair, look like a simple method. The shielded one (with surrounded meshes of fine wires) is to protect transmission, while other, the unshielded one is not for protection in transmissions through cables.   The technology was invented by Alexander Graham Bell in 1881 to solve the crosstalk problem, is simply by keeping the pairs twisted right up to the connection, so the circuit to be balancing.  

In addition, as suggested by EETimes (2018) that crosstalk can be rejected by combining a twisted-pair wire and lowpass filters. The low pass filter is technique to active component of direct current by blocking main line signals to enter direct current from transmission, and to allow the maximizing of inductances. 

The twisted cables together with lowpass filters could improve quality of telephone signals and made the cable lines could be run longer without worry of dropping signal quality. Luckily, this old invention is useful until recently such as to solve computer slowdown, using in IT cables and much more.  

References

EETimes. 2018. Design How-To Use a twist (and other popular wires) to reduce EMI/RFI.

Retrieved from https://www.eetimes.com/document.asp?doc_id=1279624

Rouse, M. 2005. Crosstalk. Retrieved from

http://searchnetworking.techtarget.com/definition/crosstalk

 

Flexibility in a New Design Network Protocol

Flexibility and Efficiency (https://www.eetimes.com) 

A new design network protocol should be flexible in principle. However, there are many issues should be address in setting up a network, some of them are Error Control and Flow Control. We will discuss these two issues in this article.

Data are transmitted from sender to receiver, the transferring of data involves many steps and levels. This process (transferring process) will cause errors at each step and level. Hence, to ensure that transferring data is success, we need to detect and correct the error. We call the process as “Error Control” process.

Two terms in error control process are error detection and then doing correction. This process will make digital data could be delivered through channels that might be unreliable. The unreliable channels occur when there is “noise’ causes interruptions (errors) during transmissions. Term of error detection will detect such interruption, then correct the errors (errors correction).  

We know that there is medium between sender and receiver in network communications, then the problem could be happened if there is different rate between sender and receiver. The rate could be higher from sender, but lower in receiver. The problem could be solved by introducing “Flow Control.”

The flow control is set up in the data link layers or higher layers. The traffic flow must be controlled no more than fair capacity. In this situation, flow control function as  akin of buffer, thus the result will produce efficiency in the communication networks.

Finally, we should take care many issues in setting up a new network. The successful to run a new network will depend on solving these issues.

Connection Oriented and Connectionless in Communication

Connection Oriented and Connectionless service (http://www.linktionary.com) 

Connection Oriented is communication mode in which connection is set up before data are transferred. As defined by Rouse (2018) that connection-oriented means data connections are established by the preliminary protocol before they are sent.  

Contrary, the connectionless has no set up for data transmission. Each data is transferred based on its information, addressed and routed.  As said by InetDaemon (2014) that “Connectionless means that no effort is made to set up a dedicated end-to-end connection.” Comparison of connection-oriented and connectionless are following: 

1.Advantages 

The advantages of Connection-Oriented and Connectionless services could be seen at Table below:

Advantages
Connection-Oriented	Connectionless
Established a session connection before data packages/frames can be sent	Every package is routed independently through the subnet
Guarantees that data will arrive in the same order as it was sent.	if something goes wrong on the subnet, no harm is done to the data which has already been sent.
The system works perfect in bi-directional communications environments	When there is little interference and plenty of speed available, then connectionless services will work very fine

The telephone network is an example of a connection-oriented service. The postal system is an example of a connectionless network service in daily life of real world. Some examples of connection-oriented packet mode communication are Asynchronous Transfer Mode, Connection-oriented Ethernet and DCCP. Some examples of a connectionless are Internet Protocol (IP), User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP).

2.Issues for both

Both connection-Oriented and Connectionless have issues (dis-advantages). The connection-Oriented introduces overhead and delays, which sometimes are undesirable. Moreover, Connectionless services sometimes will lose data due to damage in transit, it is because sender not ask receipt from the receiver.

However, I used both connection-Oriented and connectionless service in my daily life. I think to solve “delays and overhead” in the connection-Oriented service by storing the route to receiver. The other ways are to re-sequencing or to redial the services. Moreover, it is possible to solve the problem of “lose data due to damage in transit” in a connectionless network service by sending the data via a different route to the same destination.

The services, connection-oriented and connection-less have advantages and dis-advantages. The advantages could be seen at Table above (Discussion section). The connection-oriented is good for long distance, and connection-less service is good for short distance with small bandwidth.

The dis-advantages are slower for connection-oriented, and connection-less service is always not reliable as one of dis-advantages. Thus, both services are important for transferring data with their own advantages and dis-advantages.

References

InetDaemon. 2014. Connection Oriented vs. Connectionless. Retrieved from www.inetdaemon.com/tutorials/basic_concepts/communication/connection-oriented_vs_connectionless.shtml

Rouse, M. 2018. connection-oriented. Retrieved from http://searchnetworking.techtarget.com/definition/connection-oriented